The electric light industry has always been a research hotspot attracts many researchers to study on competing all over the world, and it has a very important position in the world economy. Nowadays the gas discharge light source is widely employed, and the principle of such light source is that the inner space of the lamp is evacuated prior to being fulfilled with mixed gas containing mercury, and the light is generated by means of gas discharge or emitted from the phosphor powder under the stimulation of the ultraviolet generated by the gas discharge. However, the pulsed light of gas discharge light source can easily lead to visual fatigue, and the mercury can pollute the environment. With the development of the society and the advancement of technology, it is important to research and development of energy-saving and environmental friendly, green light sources to replace traditional light sources, and it has been an important issue for the researchers to study on competing in all countries.
The organic electroluminescent device is one of the electric light sources. The organic light emission diode (OLED for short) has the properties of high brightness, wide range of material selection, low drive voltage, solid state active light-emission and the like, and also has the advantages of high definition, wide viewing angle, fast response and the like, meanwhile the OLED has excellent flexibility, thus it can be folded or bent, so it is a light source with much potential for the flexible display technology, and the development thereof is in line with the trends of the mobile communication and information display in the information age, and meets the requirement of the green lighting technology, accordingly it is currently a research focus for the researchers to study at home and abroad.
The organic electroluminescent device has a sandwich-like structure, which substantially includes an anode, an organic electroluminescent structure and a cathode, wherein the organic electroluminescent structure comprises at least one selected from the group consisting of a hole injection layer and a hole transport layer, and a light emitting layer, as well as at least one selected from the group consisting of an electron transport layer and an electron injection layer. FIG. 1 shows the structural schematic diagram of an organic electroluminescent device including all of these structures in prior art, this device comprises a transparent substrate 11 and an anode 12, an organic electroluminescent structure 13 and a cathode 14 sequentially arranged on the transparent substrate 11 and conjugated together. Wherein the organic electroluminescent structure 13 includes a hole injection layer 131, a hole transport layer 132, a light emitting layer 133, an electron transport layer 134, and an electron injection layer 135.
Up to now, researchers all over the world have improved the indicators of the device performance by selecting suitable organic materials and reasonable device structure designs, but due to the heavy driving current, low luminous efficiency, short lifetime of the light emitting device, it is desired to develop a light emitting device with small driving current, and high luminous efficiency, in order to achieve the practical use of the organic electroluminescent device.
Furthermore, the OLED in prior art can only emit light from one side of the anode or the cathode, as a result the OLED can only be the style of bottom emission or top emission. Some researchers have invented a double-sided light emitting or display OLED device with double-layer structure design, i.e. two sets of OLED light emitting or display units are combined together by means of “back to back” to achieve the double-sided light emitting or display. This kind of structure makes the configuration of the OLED device more complicated, and increases the thickness and weight thereof, and the cost is significantly increased.